Monitoring Go Applications: Libraries and Tools

Monitoring Go (Golang) Applications: A Complete Overview of Tools and Libraries

Monitoring is a critical part of operating any server application. For the Go (Golang) ecosystem, many tools have been developed to track performance, status, and errors in real time. In this article, we will cover the key libraries and approaches for monitoring Go applications, including Prometheus, expvar, pprof, and OpenTelemetry.

Why is monitoring needed for Go applications?

Go applications are often used for high-load microservices, API gateways, and background processors. Without monitoring, you risk missing:

• Memory and goroutine leaks;
• Slow requests and locks;
• Performance degradation under load;
• Connection errors to databases and external services.

1. Prometheus — the standard for metric collection

Prometheus is the de facto standard for metric collection in the Go world. The official client library prometheus/client_golang makes it easy to export metrics in Prometheus format.

Installation

go get github.com/prometheus/client_golang/prometheusgo get github.com/prometheus/client_golang/prometheus/promhttp

Example: request counter and time histogram

package main

import (    "net/http"    "time"    "github.com/prometheus/client_golang/prometheus"    "github.com/prometheus/client_golang/prometheus/promhttp")

var (    requestCount = prometheus.NewCounterVec(        prometheus.CounterOpts{            Name: "http_requests_total",            Help: "Total number of HTTP requests",        },        []string{"method", "endpoint"},    )    requestDuration = prometheus.NewHistogramVec(        prometheus.HistogramOpts{            Name:    "http_request_duration_seconds",            Help:    "Duration of HTTP requests in seconds",            Buckets: prometheus.DefBuckets,        },        []string{"method", "endpoint"},    ))

func init() {    prometheus.MustRegister(requestCount, requestDuration)}

func middleware(next http.Handler) http.Handler {    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {        start := time.Now()        next.ServeHTTP(w, r)        duration := time.Since(start).Seconds()        requestCount.WithLabelValues(r.Method, r.URL.Path).Inc()        requestDuration.WithLabelValues(r.Method, r.URL.Path).Observe(duration)    })}

func main() {    mux := http.NewServeMux()    mux.Handle("/metrics", promhttp.Handler())    mux.Handle("/", middleware(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {        w.Write([]byte("Hello, World!"))    })))    http.ListenAndServe(":8080", mux)}

After running, metrics will be available at http://localhost:8080/metrics. Prometheus will be configured to scrape from this endpoint.

2. expvar — built-in metric export

The Go standard library offers the expvar package for publishing application state variables. It requires no external dependencies.

Usage example

package main

import (    "expvar"    "net/http")

var (    requests = expvar.NewInt("requests_total")    errors   = expvar.NewInt("errors_total"))

func handler(w http.ResponseWriter, r *http.Request) {    requests.Add(1)    // Simulate an error    if r.URL.Query().Get("error") == "1" {        errors.Add(1)        w.WriteHeader(http.StatusInternalServerError)        return    }    w.Write([]byte("OK"))}

func main() {    http.HandleFunc("/debug/vars", expvar.Handler().ServeHTTP)    http.HandleFunc("/", handler)    http.ListenAndServe(":8080", nil)}

Metrics are available at the /debug/vars path in JSON format. For integration with Prometheus, you can use <